Quadrator is an electronic device for combining four source video signals into one common one, which at the same time contains thumbnails from all source video signals. The quadrator is designed for simultaneous display on one monitor of images from several analog video cameras . If four video cameras are connected to the inputs of the quad, and a monitor is connected to the output, then an image consisting of four quarters of the screen, arranged in a 2 × 2 square, will be displayed on the monitor, each of which is a small image from one of the video cameras.
The quadrator is a complex analog-to-digital device containing several ADCs , DACs , RAM, and other auxiliary electronic circuits. At the end of the 20th century, quadrants were widely used in analogue video surveillance systems as intermediate equipment. Currently, quadrators are rarely used due to the displacement of analog systems by digital ones. In digital systems, the functions of quadgers were taken over by other video surveillance system devices — digital video recorders ( DVR ) and video servers .
Also, a quad device is called an analog device whose output voltage or current is a quadratic function of the input (a special case of an analog signal multiplier)